Percutaneous devices (PD) are designed to serve a variety of clinical and biomedical research purposes. Characteristically they are objects that permanently penetrate through a defect in the skin. The histological aspects of the implant skin interfacial reactions are reviewed in this article. A short description is presented of common applications of PDs. The five presently identified interfacial failure modes are described histologically with the aid of schematic drawings. These failure modes are marsupialization, permigration , avulsion, infection, alone or in combination. Single or multiple etiological factors may be responsible for these failure modes. These factors can be surgically created skin defects around the penetrating foreign implant, epidermal healing characteristics that prevent the formation of a suitable seal at the implant-skin interface and mechanical forces that may disrupt dermal attempts to seal the interface. Eventually the interface becomes infected necessitating removal of the device. Terminology recommended for use in percutaneous device research is indexed and defined.

Fibroblasts have been shown to respond to substratum surface roughness. The change in cell size, shape and orientation of rat dermal fibroblasts (RDF) was therefore studied using smooth and microtextured silicone rubber substrata. The microtextured substrata possessed parallel surface microgrooves that ranged in width from 1.0 to 10.0/im, and were separated by ridges of 1.0 to 10.0¿¿m. The grooves were either 0.45 or 1.00^m deep. Prior to incubation, the substrata were cleaned and given a radio frequency glow discharge treatment. After surface evaluation with scanning electron microscopy and confocal laser scanning microscopy, RDF were incubated on these substrata for 5 days. During this period of incubation, the RDF were photographed on days 1, 2, 3, 4, and 5, using phase contrast microscopy. Digital image analysis of these images revealed that on surfaces with a ridge width < 4 .0 ¿tm, cells were highly orientated (<10") and elongated along the surface grooves. H Protrusions contacting the ridges specifically could be seen. If the ridge width was larger than 4.0/tm, cellular orientation was random («45") and the shape of the RDF became more circular. Furthermore, results showed that the ridge width is the most important parameter, since varying the groove width and groove depth did not affect the RDF size, shape, nor the angle of cellular orientation. ((■) 1996 Elsevier Science Limited

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In order to quantify the effect of the substrata surface topography on cellular behaviour, planar and micro-textured silicon substrata were produced and made suitable for cell culture by radio frequency glow discharge treatment. These substrata possessed parallel surface grooves with a groove and ridge width of 2.0 (SÍID02), 5.0 (SÍID05) and 10/¿m (SÍID10). Groove depth was approximately 0 .5 /m Rat dermal fibroblasts (RDFs) were cultured on these substrata and a tissue culture polystyrene control surface for 1, 2, 3, 5 and 7 days. After incubation the cell proliferation was quantified with a Coulter Counter, and RDF size, shape and orientation with digital image analysis. Cell counts proved that neither the presence of the surface grooves nor the dimension of these grooves had an effect on the cell proliferation. However, RDFs on SIID02, and to a lesser extent on SÜD05 substrata, were elongated and aligned parallel to the surface grooves. Orientation of the RDFs on SÍID10 substrata proved to be almost comparable to the SIID00 substrata. Finally, it was observed that the cells on the micro-textured substrata were capable of spanning the surface grooves. © 1996 Elsevier Science Limited Correspondence to E.T. den Braber.Most of the studies are focussed on the role of contact guidance in fundamental organogenesis phenomena like surface implanted biomaterials has only been recognized for last few years. Brunette et a l"'l0, for example, the micro-e implant surfaces to prevent epithelial downgrowth around skin-penetrating devices. Campbell and von Rocum11 described the use of surface micro-patterns as a tool to implantreduce the inflammatory response at tissue interface. Although these studies have provided important information, the fundamental mechanism of, and optimal parameters for, cell control by guidance are still unknown. In addition, the reported results are often based on subjective, qualitative observations. To surpass this lack of knowledge it is evident that a systematic study of the influence of surface topography on the cellular behaviour is required. Therefore, the objective of our studies is to approach this guidance principle in a more orderly way.In our first study12 we reported on the surface treatment on the wettability of surfaces and on 1093

To evaluate the effect of surface treatment and surface mi crotexture on cellular behavior, sm ooth and microtextured silicone substrata were produced. The microtextured sub strata possessed parallel surface grooves w ith a width and spacing of 2.0 (SilD02), 5.0 (SilDOS), and 10 [xm (SilDIO), The groove depth w as approxim ately 0.5 [xm. Subse quently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated surfaces for 1, 3, 5, and 7 days. Comparison be tween the NT and UV substrata revealed that UV treatment did not influence the contact angles and surface energies of surfaces with a similar surface topography. H owever, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT sub strata. The dim ension of the surface microevents did not influence the wettability characteristics. Cell culture exper iments revealed that RDF cell growth on UV-treated sur faces w as lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the parallel surface grooves on the SilD02 and SilDOS substrata were able to induce stronger cell orientation and alignm ent than the events on SilDIO surfaces. By combining all of our find ings, the most important conclusion was that p h ysico chemical parameters such as wettability and surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured sur faces.

The microfilaments and vinculin-containing attachment complexes of rat dermal fibroblasts (RDF) incubated on microtextured surfaces were investigated with confocal laser scanning microscopy (CLSM) and digital image analysis (DIA). In addition, depositions of bovine and endogenous fibronectin and vitronectin were studied. Smooth and microtextured silicone substrata were produced that possessed parallel surface grooves with a groove and ridge width of 2.0, 5.0, and 10.0 microns. The groove depth was approximately 0.5 micron. CLSM and DIA make it possible to visualize and analyze intracellular and extracellular proteins and the underlying surface simultaneously. It was observed that the microfilaments and vinculin aggregates of the RDFs on the 2.0 microns grooved substrata were oriented along the surface grooves after 1, 3, 5, and 7 days of incubation while these proteins were significantly less oriented on the 5.0 and 10.0 microns grooved surfaces. Vinculin was located mainly on the surface ridges on all textured surfaces. In contrast, bovine and endogenous fibronectin and vitronectin were oriented along the surface grooves on all textured surfaces. These proteins did not seem to be hindered by the surface grooves since many groove-spanning filaments were found on all the microgrooved surfaces. In conclusion, it can be said that microtextured surfaces influence the orientation of intracellular and extracellular proteins. Although results corroborate three earlier published hypotheses, they do not justify a specific choice of any one of these hypotheses.

An adequate histologic evaluation is a prerequisite for a good understanding of the behavior of tissue to implant materials. However, despite improvements in histologic sectioning techniques, few studies have used histomorphometric methods for the quantification of the tissue response. This paper discusses new simple histologic grading scales, which can be used for the fast standardized light microscopic analysis of the biocompatibility of hard and soft tissue implants. Two examples of the application of the grading scales are demonstrated.

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